Specifications

21
THEORY OF OPERATION
The host interface signals are described in the table below.
Pin
#
IS4920-xx103
(TTL RS232)
IS4920-xx38
(USB)
Description
1 232INV NC
Input: TTL RS232 polarity control
with 68k ohm pull-up. Connect to
ground for UART to UART signal
polarity. Pull up to Vin or leave
unconnected for standard TTL RS232
polarity.
2 V
in
V
in
Power: Supply voltage input
(3V to 5.5V)
3 GND GND Ground: Power and signal ground.
4 (n)RxD D-
Input: TTL Level RS232 Receive
data input. Polarity determined by Pin1
Bidirectional: USB D- Signal
5 (n)TxD <reserved>
Output: TTL Level RS232 transmits
data. Polarity Determined by Pin 1
6 (n)CTS D+
Input: TTL level Clear to Send.
Polarity configurable via software
Bidirectional: USB D+ signal
7 (n)RTS <reserved>
Output: TTL level RS232 Request to
Send. Polarity configurable via
software
8 PWRDWN PWRDWN
Output: Open drain, 100K pull up;
active high indicates that the IS4920 is
in power down mode.
9 nBEEPER nBEEPER
Output: Open drain, 100K pull up;
active low signal capable of sinking
current. PWM controlled AC signal can
be used to drive an external beeper.
10 nGoodRead nGoodRead
Output: Open drain, 100K pull up;
active low signal for sinking current of
a Good Read LED circuit.
11 nWAKE nWake
Input: 100K pull up; active low, the
signal can be used to bring the
scanner out of power-down (TTL
RS232 version only) or sleep mode
(TTL RS232 and USB versions).
12 nTrig nTrig
Input: Weak pull up; active low, the
signal can be used as a trigger input to
activate the IS4920.